This invention relates to antistats or antistatic agents and compositions that exhibit antistatic characteristics. This invention further relates to fibers, films, fabrics, coatings, or molded or blown articles comprising the compositions. In other aspects, this invention relates to a topical treatment composition and to processes for imparting antistatic characteristics to insulating materials.
Antistats or antistatic agents are used to dissipate electrostatic or static charge. Electrostatic charge buildup is responsible for a variety of problems in the processing and the use of many industrial products and materials. Electrostatic charging can cause materials to stick together or to repel one another. In addition, static charge buildup can cause objects to attract dirt and dust that can lead to fabrication or soiling problems and can impair product performance.
Sudden electrostatic discharges from insulating objects can also be a serious problem. With photographic film, these discharges can cause fogging and the appearance of artifacts. When flammable materials are present, a static electric discharge can serve as an ignition source, resulting in fires and/or explosions.
Electrostatic charge is a particular problem in the electronics industry, because modem electronic devices are extremely susceptible to permanent damage by electrostatic discharges. The buildup of electrostatic charge on insulating objects is especially common and problematic under conditions of low humidity and when liquids or solids move in contact with one another (tribocharging).
Static charge buildup can be controlled by increasing the electrical conductivity of a material. This can be accomplished by increasing ionic or electronic conductivity. The most common means of controlling static accumulation today is by increasing electrical conductivity through moisture adsorption. This is commonly achieved by adding moisture to the surrounding air (humidification) or by the use of hygroscopic antistatic agents, which are generally referred to as humectants because they rely on the adsorption of atmospheric moisture for their effectiveness. Most antistatic agents operate by dissipating static charge as it builds up; thus, static decay rate and surface conductivity are common measures of the effectiveness of antistatic agents.
Antistatic agents can be applied to the surface (external antistat) or be incorporated into the bulk (internal antistat) of the otherwise insulating material. Internal antistats are commonly employed in polymers such as plastics. Generally, internal antistats fall into one of the following classes: (1) ones that are mixed directly into a molten polymer during melt processing; (2) ones that are mixed into a polymer solution, coated, and dried, or (3) ones that dissolve into a monomer (with or without a solvent) that is subsequently polymerized.
Known antistatic agents cover a broad range of chemical classes, including organic amines and amides, esters of fatty acids, organic acids, polyoxyethylene derivatives, polyhydridic alcohols, metals, carbon black, semiconductors, and various organic and inorganic salts. Many are also surfactants and can be neutral or ionic in nature.
Many low molecular weight, neutral antistats have sufficiently high vapor pressures and thus are unsuitable for use at high temperatures (e.g., polymer melt processing) due to material losses that occur via evaporation. Many other neutral antistats have insufficient thermal stability to survive polymer melt processing or other high temperature processing conditions.
Most nonmetallic antistats are humectants that rely on the adsorption and conductivity of water for charge dissipation. Thus, their effectiveness is typically diminished at low atmospheric humidity. Because many of these antistatic agents are also water soluble, they are easily removed by exposure of the material to water (e.g., washing) and therefore are not very durable.
Metal salts of inorganic, organic, and fluoroorganic anions are also useful as antistatic agents in certain polymer compositions. Alkali metal salts are most commonly employed due to cost and toxicity considerations and to the high affinity of alkali metal cations, especially lithium, for water. But most metal salts are not compatible with polymers of moderate to low polarity, such as polypropylene, polyester, and polycarbonate. This incompatibility can result in inadequate antistat performance and/or an unacceptable reduction in physical properties or transparency in a finished polymeric article. Consequently, the use of metal salts as internal antistatic agents is generally limited to highly polar and/or hydrophilic polymer matrices.
Thus, there remains a need for antistatic agents to impart good antistatic characteristics to insulating materials in a cost effective manner and that, in particular, can be utilized as internal antistatic melt additives without suffering thermal decomposition, or causing processing problems or melt defects.
Advantageously, the present invention provides antistatic agents that exhibit good antistatic properties and that are melt processable. Briefly, in one aspect, the present invention provides antistatic agents comprising at least one polymeric salt. This salt consists of at least one cation having at least one polyoxyalkylene (POA) moiety bonded to a single ammonium center and a fluorinated anion. The cation(s) is represented by the following formula:
+N[(R1)4xe2x88x92y][[POA]R2]y
where POA is either a homopolymer or a copolymer that is random, blocked, or alternating, and POA comprises 2 to 50 units represented by the formula ((CH2)mxe2x80x2CH(R3)O) where each unit independently has mxe2x80x2, an integer from 1 to 4, and R3. R3 is independently hydrogen or a lower alkyl group (i.e., containing 1 to 4 carbon atoms). R1 is independently an alkyl, an alicyclic, an aryl, an alkalicyclic, an arylalicyclic, or an alicyclicaryl group that optionally contains one or more heteroatoms (e.g., sulfur, nitrogen, oxygen, chlorine, bromine, or fluorine). R2 is independently hydrogen, an alkyl, an alicyclic, an aryl, an alkalicyclic, an arylalicyclic, or an alicyclicaryl group that optionally contains one or more heteroatoms (e.g., sulfur, nitrogen, oxygen, chlorine, bromine, or fluorine). And y is an integer from 1 to 4.
The fluorinated anion is represented by one of the following formulae:
RfSO3xe2x88x92xe2x80x83xe2x80x83(1)
xe2x88x92O3SRf2SO3xe2x88x92xe2x80x83xe2x80x83(2)
where Rf is independently a perfluoroalkyl, fluoroalkyl, or fluoroaryl group having from 1 to about 12 carbon atoms and Rf2 is independently a perfluoroalkylene, fluoroalkylene, or fluoroarylene group having from 1 to about 10 carbon atoms.
In another aspect, the present invention provides antistatic agents as polymer melt additives for thermoplastic polymers and as additives for thermoset polymers. The antistatic agents comprise at least one polymeric salt that consists of at least one cation having at least one polyoxyalkylene moiety bonded to a single ammonium center and a fluorinated anion.
The cation(s) is represented by the following formula:
+N[(R1)4xe2x88x92y][[POA]R2]y
where POA is either a homopolymer or a copolymer that is random, blocked, or alternating, and POA comprises 2 to 50 units represented by the formula ((CH2)mxe2x80x2CH(R3)O) where each unit independently has mxe2x80x2, an integer from 1 to 4, and R3. R3 is independently hydrogen or a lower alkyl group (i.e., containing 1 to 4 carbon atoms). R1 is independently an alkyl, an alicyclic, an aryl, an alkalicyclic, an arylalicyclic, and an alicyclicaryl group that optionally contains one or more heteroatoms (e.g., sulfur, nitrogen, oxygen, chlorine, bromine, or fluorine). R2 is independently hydrogen, an alkyl, an alicyclic, an aryl, an alkalicyclic, an arylalicyclic, or an alicyclicaryl group that optionally contains one or more heteroatoms (e.g., sulfur, nitrogen, oxygen, chlorine, bromine, or fluorine). And y is an integer from 1 to 4.
The fluorinated anion is independently represented by one of the following formulae:
RfSO3xe2x88x92xe2x80x83xe2x80x83(1)
xe2x88x92O3SRf2SO3xe2x88x92xe2x80x83xe2x80x83(2)
where Rf is independently a perfluoroalkyl, fluoroalkyl, or fluoroaryl group having from 1 to about 12 carbon atoms and Rf2 is independently a perfluoroalkylene, fluoroalkylene, or fluoroarylene group having from 1 to about 10 carbon atoms.
In yet another aspect, the present invention provides topical applications of antistatic agents, where the antistatic agents comprise at least one polymeric salt. This salt consists of at least one cation having at least one polyoxyalkylene moiety bonded to a single ammonium center, and a fluorinated anion.
The cation(s) is represented by the following formula:
+N[(R1)4xe2x88x92y][[POA]R2]y
where POA is either a homopolymer or a copolymer that is random, blocked, or alternating, and POA comprises 2 to 50 units represented by the formula ((CH2)mxe2x80x2CH(R3)O) where each unit independently has mxe2x80x2, an integer from 1 to 4, and R3. R3 is independently hydrogen or a lower alkyl group (i.e., containing 1 to 4 carbon atoms). R1 is independently an alkyl, an alicyclic, an aryl, an alkalicyclic, an arylalicyclic, or an alicyclicaryl group that optionally contains one or more heteroatoms (e.g., sulfur, nitrogen, oxygen, chlorine, bromine, or fluorine). R2 is independently hydrogen, an alkyl, an alicyclic, an aryl, an alkalicyclic, an arylalicyclic, or an alicyclicaryl group that optionally contains one or more heteroatoms (e.g., sulfur, nitrogen, oxygen, chlorine, bromine, or fluorine). And y is an integer from 1 to 4.
The fluorinated anion is independently represented by one of the following formulae:
RfSO3xe2x88x92xe2x80x83xe2x80x83(1)
xe2x88x92O3SRf2SO3xe2x88x92xe2x80x83xe2x80x83(2)
where Rf is independently a perfluoroalkyl, fluoroalkyl, or fluoroaryl group having from 1 to about 12 carbon atoms and Rf2 is independently a perfluoroalkylene, fluoroalkylene, or fluoroarylene group having from 1 to about 10 carbon atoms.
In other aspects, this invention provides fiber, fabric, film, a coating, or a molded or blown article comprising the composition of the invention; processes for imparting antistatic characteristics to a substrate or an insulating material, for example, by melt addition or by topical treatment; a topical treatment composition comprising the antistat agent of the present invention; and a melt blend comprising the antistatic agent of the present invention in a thermoplastic polymer.
The present invention relates to sulfonate salts and their use as antistatic agents and these antistatic agents in compositions. Antistatic agents and antistats are used interchangeably herein. Antistatic agents preferably provide ionic conductivity, good solubility in organic media, good stability, and good blooming. Advantageously, the salts of the present invention exhibit all of these features. In addition, the salts of the present invention have good thermal stability, can be used as melt additives, and have good performance at low humidity.
The antistatic agents of the present invention can be used as additives (internal antistats) or as a coating or a topical treatment (external antistats) to impart antistatic characteristics to polymers or to other insulating materials. The insulating material is typically a thermoplastic or thermosetting polymer (preferably, a thermoplastic), and the composition can be prepared by forming a blend (preferably, a melt blend) of the components. In particular, the present invention is directed to antistatic agents and compositions comprising these antistatic agents that contain polyoxyalkylene-substituted quaternary ammonium cations having a single ammonium center and at least one fluorinated anion.
A xe2x80x9cblendxe2x80x9d is defined herein as a mixture of at least one antistat and at least one insulating material or a reactive precursor to the insulating material.
A xe2x80x9ctopical treatmentxe2x80x9d is defined herein as at least one antistat applied to the surface of a preformed insulating material or substrate, typically in a solvent or a dispersant.
Antistats
Polymeric salts suitable for use as antistats of the invention consist of at least one organic polymeric ammonium cation and a fluorinated anion. These salts can be used alone or in combination as an antistatic agent.
Polyoxyalkylene Ammonium Cation
The antistatic agent of the present invention comprises a polymeric salt. This salt consists of at least one cation having at least one polyoxyalkylene (POA) moiety bonded to a quaternary ammonium center, preferably a single cation having at least one polyoxyalkylene moiety bonded to a quaternary ammonium center.
The cation(s) is represented by the following formula:
+N[(R1)4xe2x88x92y][[POA]R2]y
where POA is either a homopolymer or a copolymer that is random, blocked, or alternating, and POA comprises 2 to 50 units represented by the formula ((CH2)mCH(R3)O) where each unit independently has m, an integer from 1 to 4, and R3. R3 is independently hydrogen or a lower alkyl group (i.e., containing 1 to 4 carbon atoms). R1 is independently an alkyl, an alicyclic, an aryl, an alkalicyclic, an arylalicyclic, or an alicyclicaryl group that optionally contains one or more heteroatoms (e.g., sulfur, nitrogen, oxygen, chlorine, bromine, or fluorine). R2 is independently hydrogen, an alkyl, an alicyclic, an aryl, an alkalicyclic, an arylalicyclic, or an alicyclicaryl group that optionally contains one or more heteroatoms (e.g., sulfur, nitrogen, oxygen, chlorine, bromine, or fluorine). And y is an integer from 1 to 4.
R1 has from 1 to about 50 carbon atoms, preferably 1 to about 20 carbon atoms, and more preferably from about 10 to about 20 carbon atoms. R2 is hydrogen or has from 1 to about 20 carbon atoms, preferably 1 to about 10 carbon atoms, and more preferably 1 to about 4 carbon atoms. R3 is hydrogen or has from 1 to about 10 carbon atoms, and preferably 1 to about 4 carbon atoms.
Synthesis of these cations is well known in the art and typically involves the alkylation of the corresponding tertiary amines using methods known in the art. Additionally, many of these cations are commercially available in the form of salts of nonfluorinated organic or inorganic anions.
Examples of specific cations include, but are not limited to, where the number of repeat units of the POA is approximate,
[(C12H25)N+(CH3)[(CH2CH2O)mH][(CH2CH2O)nH]]; (m+n=15),
[(C6H5CH2)N+(CH3)[(CH2CH2O)mH][(CH2CH2O)nH]]; (m+n=15), where C6H5CH2=benzyl,
[(C18H37)N+(CH3)[(CH2CH2O)mH][(CH2CH2O)nH]]; (m+n=15),
[(C18H37)N+(CH3)[(CH2CHO)mH][(CH2CHCH3O)nH]]; (m+n=15),
[(C12H25)N+(CH3)[(CH2CH2O)mH][(CH2CH2O)nH]]; (m+n=5),
[(C12H25)N+(CH3)2[(CH2CHCH3O)mH]]; (m=15),
[(C12H25)N+(CH3)2[(CH2CH2CH2CH2O)mH]]; (m=15),
[(C12H25)N+(CH3)2[(CH2CH2O)mH]]; (m=15),
[(C8H17)N+(CH3)2[(CH2CH2O)mH]]; (m=8),
[(C12H25)N+[(CH2CH2O)mH][(CH2CH2O)nH][(CH2CH2O)oH]]; (m+n+o=15) and
[N+[(CH2CH2O)mH][(CH2CH2O)nH][(CH2CH2O)oH][(CH2CH2O)pH]]; (m+n+o+p=20).
The fluorinated anions of the present invention are either fully fluorinated, that is perfluorinated, or partially fluorinated alkyl or aryl sulfonates (within the organic portion). Preferred fluorinated anions include those that comprise a highly fluorinated alkanesulfonate group, that is, a perfluoroalkanesulfonate group or a partially fluorinated alkanesulfonate group wherein all non-fluorine carbon-bonded substituents are bonded to carbon atoms other than the carbon atom that is directly bonded to the sulfonate group (preferably, all non-fluorine carbon-bonded substituents are bonded to carbon atoms that are more than two carbon atoms away from the sulfonate group).
Preferably, the fluorinated anion is at least about 80 percent fluorinated (that is, at least about 80 percent of the carbon-bonded substituents of the anion are fluorine atoms). More preferably, the anion is perfluorinated (that is, fully fluorinated, where all of the carbon-bonded substituents are fluorine atoms). The anions, including the preferred perfluorinated anions, can contain one or more catenated (that is, in-chain) or terminal heteroatoms such as, for example, nitrogen, oxygen, or sulfur (e.g., SF5, or SF4).
Generally, the fluorinated anion of the present invention is represented by one of the following formulae:
RfSO3xe2x88x92xe2x80x83xe2x80x83(1)
xe2x88x92O3SRf2SO3xe2x88x92xe2x80x83xe2x80x83(2)
where Rf is independently a perfluoroalkyl, fluoroalkyl, fluoroaryl group. Rf can be cyclic, or acyclic. Typically, Rf comprises from 1 to about 12 carbon atoms, preferably from 1 to about 8, and more preferably from 1 to about 4 carbon atoms. Rf2 is independently a perfluoroalkylene, fluoroalkylene, or fluoroarylene group. Rf2 comprises 1 to about 10 carbon atoms, more preferably 2 to about 6 carbon atoms. Rf2 can also be cyclic or acyclic. Fluoroaryl includes aromatic rings where some or all of the hydrogen atoms are substituted with fluorine atoms or perfluoroalkyl groups.
Representative examples of fluorinated anions of the present invention include, but are not limited to, perfluoroalkanesulfonates such as, CF3SO3xe2x88x92, C4F9SO3xe2x88x92, C6F13SO3xe2x88x92, C8F17SO3xe2x88x92, and cyclo-C6F11SO3xe2x88x92; fluoroarylsulfonates such as, 4-CF3xe2x80x94C6H4SO3xe2x88x92, 3,5-(CF3)2C6H3SO3xe2x88x92, and C6F5SO3xe2x88x92; heteroatom-containing fluoroalkanesulfonates such as CF3OCF2CF2SO3xe2x88x92, (CF3)2NCF2CF2SO3xe2x88x92, and SF5CF2CF2SO3xe2x88x92; and difunctional fluoroalkanesulfonates or fluoroarylsulfonates such as xe2x88x92O3S(CF2)3SO3xe2x88x92, xe2x88x92O3S(CF2)4SO3xe2x88x92, xe2x88x92O3S(CF2)2O(CF2)2SO3xe2x88x92, xe2x88x92O3SC6F4SO3xe2x88x92, and xe2x88x92O3SCF2CF2N(CF2CF2)2NCF2CF2SO3xe2x88x92.
The fluorinated anions can be prepared by standard methods known in the art. These methods include the anion precursor preparative methods described in the following references, the descriptions of which are incorporated herein by reference: sulfonate precursorsxe2x80x94U.S. Pat. No. 5,176,943 (Wou), U.S. Pat. No. 4,582,781 (Chen et al.), U.S. Pat. No. 3,476,753 (Hanson), and U.S. Pat. No. 2,732,398 (Brice et al.); and sulfonate precursors having catenated oxygen or nitrogen in a fluorochemical groupxe2x80x94U.S. Pat. No. 5,514,493 (Waddell et al). The fluorinated anion can be either monofunctional or multifunctional, i.e., can contain more than one sulfonate group, e.g., difunctional or trifunctional, etc. preferably, the fluorinated anion is monofunctional or difunctional, more preferably monofunctional.
Antistatic Agents
The antistats can be either solids or liquids under ambient conditions.
For use as polymer melt additives, the antistats of the present invention are preferably stable at temperatures of about 240xc2x0 C. and above (more preferably, about 280xc2x0 C. and above). In addition, for polymer melt additive applications, the antistats are preferably miscible with the insulating material at the melt processing temperature. (In other words, the thermal decomposition temperature (i.e., the temperature where there is 5 percent or more weight loss using thermal gravimetric analysis (TGA) as described in Test Method 1) of the antistats preferably is above these temperatures.)
The antistats of the present invention are represented by the following formula:
[+N[(R1)4xe2x88x92y][[POA]R2]y]u[Xxe2x88x92]
where POA is either a homopolymer or a copolymer that is random, blocked, or alternating, and POA comprises 2 to 50 units represented by the formula ((CH2)mxe2x80x2CH(R3)O) where each unit independently has mxe2x80x2, an integer from 1 to 4, and R3. R3 is independently hydrogen or a lower alkyl group (i.e., containing 1 to 4 carbon atoms). R1 is independently an alkyl, an alicyclic, an aryl, an alkalicyclic, an arylalicyclic, or an alicyclicaryl group that optionally contains one or more heteroatoms (e.g., sulfur, nitrogen, oxygen, chlorine, bromine, or fluorine). R2 is independently hydrogen, an alkyl, an alicyclic, an aryl, an alkalicyclic, an arylalicyclic, or an alicyclicaryl group that optionally contains one or more heteroatoms (e.g., sulfur, nitrogen, oxygen, chlorine, bromine, or fluorine). And y is an integer from 1 to 4 and u is an integer from 1 to 2. X is a fluorinated anion as set forth in formula (1) or (2) above. If the fluorinated anion is monofunctional, u is 1 and if the fluorinated anion is difunctional, u is 2.
Antistats of the present invention can be prepared by ion exchange or metathesis reactions, which are well known in the art. For example, a precursor ammonium salt can be combined with an acid or salt of a fluorinated sulfonate anion in aqueous solution. Upon combining, the desired product (the ammonium salt of the fluorinated sulfonate anion) separates (as a liquid or solid) or can be preferentially extracted into an organic solvent (for example, methylene chloride). The product can be isolated by filtration or by liquid/liquid phase separation, can then be washed with water to completely remove byproduct acid or salt (if present), and can then be dried thoroughly under vacuum to remove all volatiles (including water and organic solvent, if present). Similar metathesis reactions can be conducted in organic solvents (for example, acetonitrile) rather than in water, and, in this case, the salt byproduct generally preferentially precipitates, while the desired product salt remains dissolved in the organic solvent (from which it can be isolated using standard experimental techniques).
Representative examples of useful antistats include, but are not limited to, where the number of repeat units of the POA is approximate,
[(C12H25)N+(CH3)[(CH2CH2O)mH][(CH2CH2O)nH]][xe2x88x92O3SCF3]; (m+n=15),
[(C12H25)N+(CH3)[(CH2CH2O)mH][(CH2CH2O)nH]][xe2x88x92O3SC4F9]; (m+n=15),
[(C6H5CH2)N+(CH3)[(CH2CH2O)mH][(CH2CH2O)nH]][xe2x88x92O3SC4F9]; (m+n=15), where C6H5CH2=benzyl,
[(C18H37)N+(CH3)[(CH2CH2O)mH][(CH2CH2O)nH]][xe2x88x92O3SCF3]; (m+n=15),
[(C18H37)N+(CH3)[(CH2CH2O)mH][(CH2CH2O)nH]][xe2x88x92O3SC4F9]; (m+n=15),
[(C18H37)N+(CH3)[(CH2CHO)mH][(CH2CHCH3O)nH]][xe2x88x92O3SC4F9]; (m+n=15),
[(C12H25)N+CH3)[(CH2CH2O)mH][(CH2CH2O)nH]][xe2x88x92O3SCF3]; (m+n=5),
[(C8H17)N+(CH3)2[(CH2CH2O)mH]][xe2x88x92O3SCF3]; (m=15),
[(C8H17)N+(CH3)2[(CH2CH2O)mH]][xe2x88x92O3SC4F9]; (m=15),
[(C12H25)N+(CH3)2[(CH2CHCH3O)mH]][xe2x88x92O3SCF3]; (m=15),
[(C12H25)N+(CH3)2[(CH2CH2 CH2CH2O)mH]][xe2x88x92O3SCF3]; (m=15),
[(C12H25)N+(CH3)2[(CH2CH2O)mH]][xe2x88x92O3SCF3]; (m=15)
[(C8H 17)N+(CH3)2[(CH2CH2O)mH]][xe2x88x92O3SCF3]; (m=8)
[(C12H25)N+[(CH2CH2O)mH][(CH2CH2O)nH][(CH2CH2O)oH]][xe2x88x92O3SCF3]; (m+n+o=15),
[(C12H25)N+[(CH2CH2O)mH][(CH2CH2O)nH][(CH2CH2O)oH]][xe2x88x92O3SC4F9]; (m+n+o=15),
[N+[(CH2CH2O)mH][(CH2CH2O)nH][(CH2CH2O)oH][(CH2CH2O)pH]][xe2x88x92O3SCF3]; (m+n+o+p=20),
[(C12H25)N+(CH3)[(CH2CH2O)mH][(CH2CH2O)nH]]2[xe2x88x92O3SCF2CF2CF2SO3xe2x80x94]; (m+n=15),
[(C12H25)N+(CH3)[(CH2CH2O)mH][(CH2CH2O)nH]]2[xe2x88x92O3SCF2CF2N(CF2CF2)2N CF2CF2SO3xe2x88x92]; (m+n=15),
[(C12H25)N+(CH3)[(CH2CH2O)mH][(CH2CH2O)nH]][xe2x88x92O3SC6H4CF3]; (m+n=15),
[(C12H25)N+(CH3)[(CH2CH2O)mH][(CH2CH2O)nH]][xe2x88x92O3SC6F5]; (m+n=15) and
[(C12H25)N+(CH3)[(CH2CH2O)mH][(CH2CH2O)nH]]2[xe2x88x92O3SC6F4SO3xe2x88x92]; (m+n=15).
Insulating Materials
The antistatic agents of the present invention can be used in coating compositions or with various insulating materials (i.e., coated directly onto an insulating material) provided these antistatic agents are compatible with the coating and/or insulating materials. Thus, the antistatic agent preferably performs well as an antistat and does not adversely affect other properties of the coating and/or insulating materials.
The antistatic agents of the present invention are typically about 0.1 to about 50 weight percent of the antistatic coating, based on the solids in the coating.
Antistatic coatings comprising the antistatic agent of the present invention can be applied from aqueous or organic solvents (including solutions of binders) to a variety of insulating materials including photographic or x-ray film, x-ray screens, fabric, fibers, electronic components, electronic packaging, compact discs, molded or blown objects (e.g., surgical gowns), and the like. The choice of solvent varies with the insulating material.
Insulating materials that are suitable for topical treatment include materials that have relatively low surface and bulk conductivity and that are prone to static charge build-up. These materials include both synthetic and naturally-occurring polymers (or the reactive precursors thereof, for example, mono- or multifunctional monomers or oligomers) that can be either organic or inorganic in nature, as well as ceramics, glasses, and ceramic/polymer composites, ceramers, or the reactive precursors thereof.
Insulating materials that are suitable for blends with the antistatic agent of the present invention include thermoplastics, thermosets, ceramers, or reactive precursors.
Suitable synthetic polymers (which can be either thermoplastic or thermoset) include commodity plastics such as, for example, poly(vinyl chloride), polyethylenes (high density, low density, very low density), polypropylene, polybutylene, and polystyrene; engineering plastics such as, for example, polyesters (including, for example, poly(ethylene terephthalate) and poly(butylene terephthalate), polyamides (aliphatic, amorphous, aromatic), polycarbonates (for example, aromatic polycarbonates such as those derived from bisphenol A), polyoxymethylenes, polyacrylates and polymethacrylates (for example, poly(methyl methacrylate)), some modified polystyrenes (for example, styrene-acrylonitrile (SAN) and acrylonitrile-butadiene-styrene (ABS) copolymers), high-impact polystyrenes (SB), fluoroplastics, and blends such as poly(phenylene oxide)-polystyrene and polycarbonate-ABS; high-performance plastics such as, for example, liquid crystalline polymers (LCPs), polyetherketone (PEK), polysulfones, polyimides, and polyetherimides; thermosets such as, for example, alkyd resins, phenolic resins, amino resins (for example, melamine and urea resins), epoxy resins, unsaturated polyesters (including so-called vinyl esters), polyurethanes, allylics (for example, polymers derived from allyldiglycolcarbonate), fluoroelastomers, and polyacrylates; and the like and blends thereof. Suitable naturally occurring polymers include proteinaceous materials such as silk, wool, and leather; and cellulosic materials.
Thermoplastic and thermoset polymers, including those described above, are preferred insulating materials, as these polymers can either be topically treated with the antistat or can be combined with the antistat (in bulk) to form a blend. Melt processing of the antistat into a thermoplastic polymer is preferred, because it eliminates the use of hazardous solvents and VOCs. Preferably, the thermoplastic polymers are melt processable at elevated temperatures, for example, above about 150xc2x0 C. (more preferably, above about 240xc2x0 C.; even more preferably, above about 280xc2x0 C.). Preferred thermoplastic polymers include, for example, polypropylene, polyethylene, polybutylene, copolymers of ethylene and one or more alpha-olefins (for example, poly(ethylene-butene) and poly(ethylene-octene)), polyesters, polyurethanes, polycarbonates, polyetherimides, polyimides, polyetherketones, polysulfones, polystyrenes, ABS copolymers, polyamides, fluoroelastomers, and blends thereof. More preferred are polypropylene, polyethylene, polyesters, poly(ethylene-octene), polyurethanes, polycarbonates, and blends thereof, with polypropylene, polyethylene, polybutylene, poly(ethylene-octene), poly(ethylene-butene), polyurethanes, and blends thereof being most preferred.
The antistatic agent can also be blended with monomers, curable oligomers, or curable polymers followed by polymerization or curing to form a crosslinked thermoset polymer containing the antistat. Preferred thermoset polymers include polyurethanes, epoxy resins, and unsaturated polyesters.
The antistatic agent of the present invention can further be applied to an insulating material using techniques known in the art such as, but not limited to, dip coating, spray coating, swirl coating, spin coating, extrusion hopper coating, curtain coating, gravure coating, air knife coating, and the like. The coating thickness varies as a function of the insulating material.
Preparation and Use of Composition
Preferably, the composition of the invention can be prepared by (a) combining at least one antistat and at least one thermoplastic polymer (optionally, along with other additives) and then melt processing the resulting combination; or (b) combining at least one antistat and at least one thermosetting polymer or ceramer or the reactive precursors thereof (optionally, along with other additives) and then allowing the resulting combination to cure, optionally with the application of heat or actinic radiation. Alternative processes for preparing the composition include, for example, (c) applying a treatment composition comprising at least one antistat to at least a portion of at least one surface of at least one insulating material; (d) dissolving at least one antistat and at least one insulating material in at least one solvent and then casting or coating the resulting solution and allowing evaporation of the solvent, optionally with the application of heat; and (e) combining at least one antistat and at least one monomer (optionally, along with other additives including solvent) and then allowing polymerization of the monomer to occur, optionally with the application of heat or actinic radiation.
To form a melt blend by melt processing, the antistat(s) can be, for example, intimately mixed with pelletized or powdered polymer and then melt processed by known methods such as, for example, molding, melt blowing, melt spinning, or melt extrusion. The antistat(s) can be mixed directly with the polymer, or can be mixed with the polymer in the form of a xe2x80x9cmaster batchxe2x80x9d (concentrate) of the antistat(s) in the polymer. If desired, an organic solution of the antistat(s) can be mixed with powdered or pelletized polymer, followed by drying (to remove solvent) and then by melt processing. Alternatively, the antistat(s) can be injected into a molten polymer stream to form a blend immediately prior to, for example, extrusion into fibers or films or molding into articles.
After melt processing, an annealing step can be carried out to enhance the development of antistatic characteristics. In addition to, or in lieu of, this annealing step, the melt processed combination (for example, in the form of a film or a fiber) can also be embossed between two heated rolls, one or both of which can be patterned. An annealing step typically is conducted below the melt temperature of the polymer (for example, in the case of polyamide, at about 100-220xc2x0 C. for a period of about 30 seconds to about 5 minutes). In some cases, the presence of moisture can improve the effectiveness of the antistat(s), although the presence of moisture is not necessary in order for antistatic characteristics to be obtained.
The antistat(s) can be added to thermoplastic or thermosetting polymer (or, alternatively, to other insulating material) in amounts sufficient to achieve the desired antistatic and repellency properties for a particular application. The amounts can be determined empirically and can be adjusted as necessary or desired to achieve the antistatic properties without compromising the properties of the polymer (or other insulating material). Generally, the antistat(s) can be added in amounts ranging from about 0.1 to about 50 percent by weight (preferably, from about 0.5 to about 10 percent; more preferably, from about 0.75 to about 2.0 percent) based on the weight of polymer (or other insulating material).
In topical treatment of an insulating material, the antistat(s) can be employed alone or in the form of aqueous suspensions, emulsions, or solutions, or as organic solvent (or organic solvent/water) solutions, suspensions, or emulsions. Useful organic solvents include chlorinated hydrocarbons, alcohols (for example, isopropyl alcohol), esters, ketones (for example, methyl ethyl ketone), and mixtures thereof. Generally, the solvent solutions can contain from about 0.1 to about 50 percent, or even up to about 90 percent, by weight non-volatile solids (based on the total weight of the components). Aqueous suspensions, emulsions, or solutions are generally preferred and generally can contain a non-volatile solids content of about 0.1 to about 50 percent, preferably, about 1 to about 10 percent, by weight (based on the total weight of the components). Alternatively, however, topical treatment can be carried out by applying (to at least a portion of at least one surface of at least one insulating material) a topical treatment composition that comprises at least one antistat that is liquid at the use or treatment temperature. This topical treatment process can involve the use of the neat liquid antistat(s), without added solvent, and is thus preferred from an environmental perspective over the use of organic solvent solutions of the antistat(s).
The topical treatment compositions comprising the antistat(s) can be applied to an insulating material by standard methods such as, for example, spraying, padding, dipping, roll coating, brushing, or exhaustion (optionally followed by the drying of the treated material to remove any remaining water or solvent). The material can be in the form of molded or blown articles, sheets, fibers (as such or in aggregated form, for example, yarn, toe, web, or roving, or in the form of fabricated textiles such as carpets), woven and nonwoven fabrics, films, etc.
The topical treatment compositions can be applied in an amount sufficient to achieve the desired antistatic properties for a particular application. This amount can be determined empirically and can be adjusted as necessary or desired to achieve the antistatic properties without compromising the properties of the insulating material.
Any of a wide variety of constructions can be made from the composition of the invention, and these constructions find utility in any application where some level of antistatic characteristic is required. For example, the composition of the invention can be used to prepare films and molded or blown articles, as well as fibers (for example, melt-blown or melt-spun fibers, including microfibers) that can be used to make woven and nonwoven fabrics. These films, molded or blown articles, fibers, and fabrics exhibit antistatic characteristics under a variety of environmental conditions and can be used in a variety of applications.
For example, molded articles comprising the composition of the invention can be prepared by standard methods (for example, by high temperature injection molding) and are particularly useful as, for example, headlamp covers for automobiles, lenses (including eyeglass lenses), casings or circuit boards for electronic devices (for example, computers), screens for display devices, windows (for example, aircraft windows), and the like. Films comprising the composition of the invention can be made by any of the film making methods commonly employed in the art. These films can be nonporous or porous (the latter including films that are mechanically perforated), with the presence and degree of porosity being selected according to the desired performance characteristics. The films can be used as, for example, photographic films, transparency films for use with overhead projectors, tape backings, substrates for coating, and the like.
Fibers comprising the composition of the invention can be used to make woven or nonwoven fabrics that can be used, for example, in making medical fabrics, medical and industrial apparel, fabrics for use in making clothing, home furnishings such as rugs or carpets, and filter media such as chemical process filters or respirators. Nonwoven webs or fabrics can be prepared by processes used in the manufacture of either melt-blown or spun bonded webs. For example, a process similar to that described by Wente in xe2x80x9cSuperfine Thermoplastic Fibers,xe2x80x9d Indus. Eng""g Chem. 48, 1342 (1956) or by Wente et al. in xe2x80x9cManufacture of Superfine Organic Fibers,xe2x80x9d Naval Research Laboratories Report No. 4364 (1954) can be used. Multi-layer constructions made from nonwoven fabrics enjoy wide industrial and commercial utility, for example, as medical fabrics. The makeup of the constituent layers of such multi-layer constructions can be varied according to the desired end-use characteristics, and the constructions can comprise two or more layers of melt-blown and spun bonded webs in many useful combinations such as those described in U.S. Pat. No. 5,145,727 (Potts et al.) and U.S. Pat. No. 5,149,576 (Potts et al.), the descriptions of which are incorporated herein by reference.
The antistat(s) used in the composition of the invention can also find utility as additives to coatings (for example, polymer or ceramer coatings). These coatings can be antistatic and can be used in the photographic industry or as protective coatings for optical or magnetic recording media.
If desired, the composition of the invention can further contain one or more conventional additives commonly used in the art, for example, dyes, pigments, antioxidants, ultraviolet stabilizers, flame retardants, surfactants, plasticizers, tackifiers, fillers, and mixtures thereof. In particular, performance enhancers (for example, polymers such as polybutylene) can be utilized to improve the antistatic characteristics in, for example, melt additive polyolefin applications.